U.S. patent application number 11/493451 was filed with the patent office on 2008-01-31 for apparatus and method for increasing the hydrogen content of recirculated exhaust gas in fuel injected engines.
Invention is credited to Terrence F. Alger, Jess W. Gingrich.
Application Number | 20080022680 11/493451 |
Document ID | / |
Family ID | 38984749 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080022680 |
Kind Code |
A1 |
Gingrich; Jess W. ; et
al. |
January 31, 2008 |
Apparatus and method for increasing the hydrogen content of
recirculated exhaust gas in fuel injected engines
Abstract
A water-gas shift catalyst in an exhaust gas recirculation
system of either a naturally-aspirated or forced induction
fuel-injected internal combustion engine uses a water-gas shift
reaction to increase the amount of hydrogen in recirculated exhaust
gas.
Inventors: |
Gingrich; Jess W.; (San
Antonio, TX) ; Alger; Terrence F.; (San Antonio,
TX) |
Correspondence
Address: |
Ted D. Lee;Gunn & Lee, P.C.
Suite 1500, 700 N. St. Mary's St.
San Antonio
TX
78205
US
|
Family ID: |
38984749 |
Appl. No.: |
11/493451 |
Filed: |
July 26, 2006 |
Current U.S.
Class: |
60/605.2 ;
60/600 |
Current CPC
Class: |
Y02T 10/121 20130101;
F02M 26/36 20160201; F02B 37/00 20130101; F02M 26/05 20160201; F02B
29/0406 20130101; F02M 26/23 20160201; F02M 26/06 20160201; F02M
26/35 20160201; Y02T 10/12 20130101; F02M 26/43 20160201; F02M
25/12 20130101; F01N 13/107 20130101 |
Class at
Publication: |
60/605.2 ;
60/600 |
International
Class: |
F02B 33/44 20060101
F02B033/44; F02D 23/00 20060101 F02D023/00 |
Claims
1. An apparatus for increasing the amount of hydrogen in the
recirculated exhaust gas of a fuel-injected engine having a
plurality of combustion chambers, an intake manifold in fluid
communication with said plurality of combustion chambers, and an
exhaust manifold in fluid communication with at least one of said
combustion chambers, comprising: a fuel injection system adapted to
inject controlled amounts of fuel into each of said combustion
chambers; an exhaust gas recirculation system having an inlet in
controlled fluid communication with said exhaust manifold and an
outlet in fluid communication with said intake manifold; a
water-gas shift catalyst disposed in said exhaust gas recirculation
system and having an inlet and an outlet; and an exhaust gas
recirculation flow control valve disposed at a position sufficient
to control the flow of exhaust gas through said exhaust gas
recirculation system and having an inlet in fluid communication
with said exhaust manifold of the engine and an outlet in fluid
communication with the inlet of said water-gas shift catalyst.
2. The apparatus for increasing the amount of hydrogen in the
recirculated exhaust gas of a fuel-injected engine, as set forth in
claim 1, wherein said apparatus includes a compressor having an
inlet in fluid communication with a source of ambient air and an
outlet in fluid communication with said intake manifold.
3. The apparatus for increasing the amount of hydrogen in the
recirculated exhaust gas of a fuel-injected engine, as set forth in
claim 2, wherein the outlet of said water-gas shift catalyst is in
fluid communication with the inlet of said compressor.
4. The apparatus for increasing the amount of hydrogen in the
recirculated exhaust gas of a fuel-injected engine, as set forth in
claim 2, wherein said exhaust gas recirculation system includes a
heat exchanger having an inlet in fluid communication with the
outlet of said compressor and an outlet in fluid communication with
said intake manifold.
5. The apparatus for increasing the amount of hydrogen in the
recirculated exhaust gas of a fuel-injected engine, as set forth in
claim 4, wherein the outlet of said water-gas shift catalyst is in
direct fluid communication with the inlet of said heat
exchanger.
6. A method for increasing the amount of hydrogen in the
recirculated exhaust gas of a fuel-injected engine having a
plurality of combustion chambers, an intake manifold in fluid
communication with said plurality of combustion chambers, and an
exhaust manifold in fluid communication with at least one of said
combustion chambers, comprising: providing an exhaust gas
recirculation system having an inlet in fluid communication with
said exhaust manifold and an outlet in fluid communication with
said intake manifold; disposing a water-gas shift catalyst in said
exhaust gas recirculation system; inducting a mixture of
recirculated exhaust gas and ambient air into the combustion
chambers of said engine; controllably injecting fuel into the
combustion chambers of said engine, combusting the fuel, and
producing an exhaust gas; controllably circulating at least a
portion of said exhaust gas through the water-gas shift catalyst
disposed in said exhaust gas recirculaton system and forming a
hydrogen enriched exhaust gas; and directing said hydrogen enriched
exhaust gas into said intake manifold of the engine.
7. The method for increasing the amount of hydrogen in the
recirculated exhaust gas of a fuel-injected engine as set forth in
claim 6, wherein said exhaust gas recirculation system includes an
exhaust gas flow control valve and said controllably circulating at
least a portion of said exhaust gas through the water-gas shift
catalyst includes modulating said exhaust gas flow control
valve.
8. The method for increasing the amount of hydrogen in the
recirculated exhaust gas of an engine, as set forth in claim 6,
wherein said engine has a first exhaust manifold in fluid
communication with at least one of said combustion chambers and a
second exhaust gas manifold in fluid communication with other ones
of.said plurality of combustion chambers, said inlet of the exhaust
gas recirculation system being in fluid communication only with
said first exhaust manifold, and said controllably circulating at
least a portion of said exhaust gas through the water-gas shift
catalyst includes controllably only circulating at least a portion
of the exhaust gas from said first exhaust manifold through the
water-gas shift catalyst.
9. The method for increasing the amount of hydrogen in the
recirculated exhaust gas of an engine, as set forth in claim 6,
wherein said exhaust gas recirculation system includes a heat
exchanger and said controllably circulating at least a portion of
said exhaust gas through the water-gas shift catalyst disposed in
said exhaust gas recirculaton system and forming a hydrogen
enriched exhaust gas includes passing said hydrogen enriched
exhaust gas through said heat exchanger prior to directing the
hydrogen enriched exhaust gas into the intake manifold of the
engine.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] This invention relates generally to an apparatus and method
for increasing the amount of hydrogen in the recirculated exhaust
gas of fuel-injected engines, and more particularly to such an
apparatus and method in which at least a portion of the
recirculated exhaust gas is passed through a water-gas shift
catalyst.
[0003] 2. Background Art
[0004] With continuing federal, state and consumer demands for
engines to achieve higher efficiency and lower emissions,
manufacturers are continually developing control strategies to
improve engine performance. One such proven technique is
hydrogen-enriched fuel, for example, Hythane and Syngas. Increased
levels of hydrogen (H.sub.2) enable stable engine operation under
dilute air/fuel ratio conditions and accelerate the combustion
event relative to the base fuel. Engine-knock tolerance also
increases with accelerated combustion, allowing the engine to
operate at higher compression ratios, resulting in higher
efficiencies.
[0005] U.S. Pat. No. 5,339,634 granted Aug. 23, 1994 to Nigel F.
Gale, et al. and assigned to the assignee of the present invention,
describes a system and process for enhancing the hydrogen content
of recirculated exhaust gas in carburetted reciprocating and gas
turbine engines. Carburetted engines require a carburetor instead
of fuel injectors. In the Gale, et al. patent, separate carburetors
are required to vaporize fuel and mix it with air prior to the
introduction of specifically-formed air/fuel mixtures into
respective combustion chambers of the engine. One of the
carburetors is controlled to provide a rich air/fuel mixture which,
after combustion in one or more dedicated combustion chambers, is
directed through a water-gas shift catalyst to provide a
hydrogen-enriched exhaust gas. The hydrogen-enriched exhaust gas is
mixed with air and fuel in a second carburetor and inducted into
the remaining combustion chambers of the engine. The described
arrangement is not applicable to fuel-injected engines which do not
pre-mix air and fuel prior to introduction into the combustion
chambers of an engine.
[0006] U.S. Pat. No. 6,742,307 B2 granted Jun. 1, 2004 to Bowie G.
Keefer, et al. for FUEL COMPOSITION MODICATION FOR INTERNAL
COMBUSTION ENGINES describes a process that uses a rotary pressure
swing adsorption apparatus to reform exhaust gas produced by an
engine. The primary function of the process is to provide
oxygen/nitrogen enrichment of a fresh charge introduced into one or
more combustion chambers of the engine. In a sub-process, hydrogen
is produced as a fuel for use in a fuel cell. Any excess hydrogen
can be routed into the engine intake manifold to aid lean burn
combustion.
[0007] Fuel reforming is also used to increase the hydrogen content
of the reformed fuel. Fuel reforming, as described in U.S. Pat. No.
6,823,852 D2, granted Nov. 30, 2004, to R. Kirk Collier, Jr., for a
LOW-EMISSION INTERNAL COMBUSTION ENGINE is used to supply H.sub.2O
and heat to a reactor for the purpose of reforming fuel into
lighter components. However, fuel reforming is a highly exothermic
process that causes a decrease in net thermal efficiency when
compared with an engine system that does not require fuel reforming
to produce hydrogen.
[0008] The present invention is directed to overcoming the problems
associated with hydrogen enriched combustion in fuel-injected
engines. It is desirable to provide a hydrogen-enriched intake
air/recirculated exhaust gas charge to the combustion chambers of
fuel injected engines. It is desirable to have a hydrogen
enrichment process that can be incorporated into both naturally
aspirated and forced-induction fuel-injected engine control
strategies that use exhaust gas recirculation (EGR). Moreover, it
is desirable to have a process that advantageously uses the low
minimum ignition energy and wide flammability range of hydrogen to
increase the ignitability of very dilute recirculated exhaust
gas/air mixtures into which fuel is injected immediately prior to
combustion, while simultaneously increasing engine exhaust EGR
tolerance.
SUMMARY OF THE INVENTION
[0009] In accordance with one aspect of the present invention, an
apparatus for increasing the amount of hydrogen in the recirculated
exhaust gas of an engine having a plurality of combustion chambers,
an intake manifold, and an exhaust manifold in fluid communication
with at least one of the combustion chambers, includes a fuel
injection system, and an exhaust gas recirculation (EGR) system.
The EGR system has an inlet in fluid communication with the exhaust
manifold and an outlet in fluid communication with the intake
manifold. The apparatus also includes a water-gas shift catalyst
disposed in the EGR system and an exhaust gas recirculation flow
control valve positioned to control exhaust gas flow through the
EGR system. The inlet of the EGR flow control valve is in fluid
communication with the exhaust manifold of the engine and the
outlet of the EGR valve is in fluid communication with the inlet of
the water-gas shift catalyst.
[0010] Other features of the apparatus for increasing the amount of
hydrogen in the recirculated exhaust gas of a fuel-injected engine
in accordance with the present invention, include the apparatus
having a compressor with an inlet in fluid communication with a
source of ambient air, and in one embodiment also in direct fluid
communication with the outlet of the water-gas shift catalyst.
[0011] Another feature of the present invention includes the
apparatus for increasing the amount of hydrogen in the recirculated
exhaust gas of a fuel-injected engine having a heat exchanger with
an inlet in fluid communication with an outlet of the compressor,
and, in one embodiment, is also in direct fluid communication with
the outlet of the water-gas shift catalyst.
[0012] In accordance with another aspect of the present invention,
a method for increasing the amount of hydrogen in the recirculated
exhaust gas of a fuel-injected engine that has a plurality of
combustion chambers, an intake manifold and an exhaust manifold,
includes providing an exhaust gas recirculation system that has an
inlet in fluid communication with the exhaust manifold and an
outlet in fluid communication with the intake manifold. The method
further includes disposing a water-gas shift catalyst in the
exhaust gas recirculation system. A mixture of recirculated exhaust
gas and ambient air is inducted into the combustion chambers. Fuel
is controllably injected, burned and discharged into the exhaust
manifold. A portion of the discharged exhaust gas is controllably
circulated through the water-gas shift catalyst wherein a
hydrogen-enriched exhaust gas is formed and subsequently directed
into the intake manifold of the engine.
[0013] The method for increasing the amount of hydrogen in the
recirculated exhaust gas of a fuel-injected engine, in accordance
with the present invention, also includes the engine having a first
exhaust manifold in communication with at least one of the
combustion chambers and a second exhaust manifold in fluid
communication with other combustion chambers. The inlet of the
exhaust gas recirculation system is in fluid communication with
only the first exhaust manifold. The method further includes
controllably recirculating at least a portion of the exhaust gas
from the first exhaust manifold, through the exhaust gas
recirculation system, the water-gas shift catalyst, and to the
intake manifold.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] A more complete understanding of the apparatus and method
for increasing the amount of hydrogen in the recirculated exhaust
gas of a fuel-injected engine may be had by reference to the
following detailed description when taken in conjunction with the
accompanying drawings, wherein:
[0015] FIG. 1 is a three-dimensional view of a representative
forced induction fuel-injected engine adapted for increasing the
amount of hydrogen in recirculated exhaust gas, in accordance with
the present invention;
[0016] FIG. 2 is a simplified schematic diagram of the
fuel-injected engine illustrated in FIG. 1;
[0017] FIG. 3 is a simplified schematic diagram of an alternate
embodiment of a forced-induction fuel-injected engine adapted for
increasing the amount of hydrogen in recirculated exhaust gas of an
engine, in accordance with the present invention; and,
[0018] FIG. 4 is a simplified schematic diagram of a naturally
aspirated fuel-injected engine adapted for increasing the amount of
hydrogen in the recirculated exhaust gas of an engine in accordance
with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] A first preferred embodiment of the present invention is
illustrated in FIGS. 1 and 2 with reference to a representative
fuel-injected engine internal combustion engine generally indicated
by the reference numeral 10. "Fuel-injected" as used in the
following discussion and claims means an engine that uses no
carburetor but sprays fuel either directly into the combustion
chambers of the engine or into the intake manifold just ahead of
the combustion chamber. Generally, fuel injected engines use
electronic sensing devices to control fuel injectors which inject
closely controlled amounts of fuel. For purposes of the following
discussion, the engine 10 may be either a naturally aspirated or
forced induction fuel-injected engine fueled with gasoline, natural
gas, or other spark-ignitable hydrocarbon fuel, or a diesel engine
fueled with diesel, bio-diesel, or other compression-ignitable
fuel. Naturally aspirated engines take in air at normal pressure,
i.e., they are not turbocharged or supercharged as is the case with
forced induction engines.
[0020] In the first-described embodiment of the present invention,
the engine 10 has a high pressure exhaust gas recirculation (EGR)
system, generally represented by the reference numeral 12.
Importantly, hydrogen (H.sub.2) is produced in the EGR system 12 by
a water-gas shift reaction. The water-gas shift is a slightly
exothermic reaction in which water vapor (H.sub.2O) and carbon
monoxide (CO) produce hydrogen (H.sub.2) and carbon dioxide
(CO.sub.2). The water-gas shift reaction is represented by the
following reaction formula:
CO+H.sub.2O.fwdarw.CO.sub.2+H.sub.2
[0021] In the present invention, the water-gas shift reaction is
accelerated with a catalyst, discussed below in greater detail, and
can be incorporated into current engine control strategies using
exhaust gas recirculation. Importantly, in the present invention,
as exhaust gas recirculation levels increase, the amount of H.sub.2
will increase proportionately. Hydrogen has low minimum ignition
energy and a wide flammability range. The combination of low
minimum ignition energy and wide flammability increases the
ignitability of very dilute mixtures, thereby increasing the
engine's tolerance for relative amounts of recirculated exhaust
gas. Higher levels of exhaust gas recirculation will increase part
load brake efficiency due to a decrease in pumping losses.
Furthermore, it is known that high EGR levels reduce NO.sub.X
emissions by a significant amount, for example, up to ten percent
(10%) of the base engine NO.sub.X emission. Because H.sub.2 is
produced in the exhaust gas recirculation system 12, any engine 10
producing CO and H.sub.2O can beneficially make use of the present
invention. Generally, an engine produces more CO and H.sub.2O with
air/fuel ratios at, or richer than, a stoichiometric mixture.
[0022] Turning now to the illustrated embodiment represented in
FIGS. 1 and 2, the forced induction, fuel-injected engine 10 has an
intake duct 14 through which intake air is drawn and subsequently
inducted into an intake manifold 16 and then into a plurality of
combustion chambers 18 by a compressor stage 20 of a turbocharger
22. In the embodiment illustrated in FIG. 1, intake air discharged
from the compressor 20 is directed through a heat exchanger 24,
sometimes also referred to as an intercooler or a charge cooler, by
which the intake air and recirculated exhaust gas charge is cooled
prior to introduction into the intake manifold 16 and subsequently
into the combustion chambers 18. Fuel is introduced by way of a
fuel injection system, represented by a fuel line 26, which
controllably injects fuel through injection nozzles 27 directly
into respective combustion chambers 18. Alternatively, the fuel
injectors 27 may be positioned in the intake port of, or in
otherwise close proximity to, a respective combustion chamber
18.
[0023] After combustion of the fuel in the combustion chambers 18,
the products of combustion are discharged into an exhaust manifold
28. The exhaust gas is then directed through a turbine stage 30 of
the turbo charger 22 into an exhaust duct 32. Typically, the engine
may also have a three-way catalyst 34, and/or other exhaust gas
aftertreatment devices, as illustrated in FIG. 1, through which
exhaust gas passes prior to discharge into the ambient
environment.
[0024] For purposes of carrying out the method embodying the
present invention, the engine 10 uses the water gas shift catalyst
38 in the exhaust gas recirculation system 12 to increase the
hydrogen content in the EGR. More specifically, a portion of the
exhaust gas passing through the exhaust manifold 28 is directed
through the exhaust duct 32 to an exhaust gas recirculation flow
control valve 36, which regulates the relative portion of the
exhaust gas directed through the EGR system 12. Importantly, after
passing through the EGR flow control valve 36, the recirculated
exhaust gas is directed through an exhaust gas recirculation
water-gas shift catalyst 38 in which a water-gas shift reaction
takes place, resulting in an increase in the hydrogen content of
the gas. After passing from an outlet 40 of the water-gas shift
catalyst, the hydrogen-enriched exhaust gas, along with ambient
air, is directed into an inlet 42 of the compressor 20 where it is
compressed and subsequently discharged from an outlet 44 of the
compressor to an inlet 46 of the heat exchanger 24. After being
cooled in the heat exchanger 24, the ambient air/hydrogen enriched
recirculated exhaust gas is directed through an outlet 48 of the
heat exchanger into the intake manifold 16 and then into respective
combustion chambers 18 of the engine 10.
[0025] Various catalysts suitable for use in the water-gas shift
reaction, incorporated in the exhaust gas recirculation system 12
of the present invention, are described in the above-discussed U.S.
Pat. No. 5,339,634 granted to Gale et al. and in U.S. Pat. No.
6,713,040 B2 granted Mar. 30, 2004 to ShabbirAhmed, et al. for a
METHOD FOR GENERATING HYDROGEN FOR FUEL CELLS.
[0026] As noted above, CO and H.sub.2O are necessary constituents
of the exhaust gas stream in order to promote the water-gas shift
reaction. The relative amounts of CO and H.sub.2O in an exhaust gas
stream are strongly dependent upon the air/fuel ratio of the
combusted air/fuel charge. Greater amounts of CO and H.sub.2O will
be generated if the air/fuel ratio is rich of stoichiometric, i.e.,
having an equivalence ratio greater than 1. Thus, in the first
preferred embodiment illustrated in FIGS. 1 and 2, the engine is
desirably operated with an air/fuel ratio that is at stoichiometric
or richer to provide significant amounts of CO and H.sub.2O in the
recirculated exhaust gas.
[0027] However, many fuel-injected engines are designed, for
purposes of efficiency and emissions control, to operate in a
lean-burn combustion mode, i.e., with an air/fuel equivalence ratio
less than 1, in which relatively lesser amounts of CO and H.sub.2O
are available. A second embodiment of the present invention, in
which a forced induction fuel-injected engine 10' designed for
lean-burn operation, is illustrated in FIG. 3. In this embodiment,
a low pressure exhaust gas recirculation system 12' is in fluid
communication with only a predetermined portion of the combustion
chambers, respectively identified by reference number 50. The
number of designated combustion chambers 50 from which exhaust gas
is recirculated may be only a single combustion chamber or three
chambers as illustrated in FIG. 3. The number of combustion
chambers 50 associated with the exhaust gas recirculation system
12' will depend on the exhaust gas recirculation requirements of an
engine. Importantly, the designated combustion chambers 50 can be
operated in a rich, or slightly rich, combustion mode while
operating the remaining cylinders 18' in a lean-burn combustion
mode.
[0028] The products of rich, or slightly rich, combustion are
directed from the combustion chambers 50 through a first exhaust
manifold 52 and thence through an exhaust gas recirculation flow
control valve 36' to an EGR water-gas shift catalyst 38'. After
passing through the water-gas shift catalyst 38', the
hydrogen-enriched exhaust gas is directed, along with compressed
inlet air discharged from the compressor 20, through the heat
exchanger 24' into the intake manifold 16' and then into respective
combustion chambers 18', 50. The non-designated combustion chambers
18' are in fluid communication with a second exhaust manifold 54
and are not part of the exhaust gas recirculation system 12'.
[0029] In a third embodiment of the present invention, a
naturally-aspirated fuel-injected engine 10'' is schematically
illustrated in FIG. 4. In this embodiment, exhaust gas is
discharged from an exhaust manifold 28'' and a portion, controlled
by an exhaust gas recirculation control valve 36'', is directed
through a water-gas shift catalyst 38'' where the water-gas shift
reaction increases the hydrogen content of the recirculated exhaust
gas. The hydrogen-enriched exhaust gas is then passed through a
heat exchanger 24'' and cooled prior to mixing with intake air in
an intake duct 14''. The mixture of hydrogen-enriched exhaust gas
and intake-air is directed into an intake manifold 16'' and
subsequently inducted into the combustion chambers 18''.
Alternatively, only the exhaust gas from one or more designated
combustion chambers may be recirculated using separate exhaust
manifolds as illustrated in FIG. 3.
[0030] Importantly, the hydrogen enrichment of recirculated exhaust
gas in accordance with the present invention does not impair the
performance of downstream exhaust gas aftertreatment systems, such
as three-way catalysts. Also, fuel injection enables precise
air/fuel ratio control to regulate the recirculated water-gas shift
reaction using global air/fuel ratio control, as illustrated in
FIGS. 1, 2 and 4, or individual cylinder air/fuel ratio control, as
illustrated in FIG. 3. Advantageously, fuel injection enables a
portion of the combustion chambers of an engine to be operated at
an equivalence ratio just rich of stoichiometric, for example about
1.05, thereby enabling the production of significant amounts of
H.sub.2 through the water-gas shift reaction. In such an
arrangement, the exhaust from the combustion chambers operating
just rich of stoichiometric are used as the recirculated exhaust
gas for all combustion chambers. It should also be recognized that
minor deviations in global air/fuel ratio control, and subsequent
hydrogen production, could also be used to assist qualitative
engine performance characteristics, such as drivability and
transient response with little penalty on thermal efficiency.
[0031] From the above description, it can be seen that the present
invention uses a water-gas shift catalyst to generate an intake
charge composition for fuel-injected engines that can beneficially
increase knock resistance and engine exhaust gas recirculation
tolerance. Furthermore, the use of the water-gas shift reaction in
the recirculated exhaust gas provides an intake
air/hydrogen-enriched recirculated exhaust gas composition that
increases the ignitability, flammability, and flame speed of the
intake charge in fuel-injected engines. Advantageously, the
water-gas shift reaction in the recirculated exhaust gas
simultaneously decreases the CO and H.sub.2O in the exhaust gas
while increasing the more benign CO.sub.2 content of the engine
exhaust.
[0032] Although the present invention is described in terms of
preferred illustrated embodiments, those skilled in the art will
recognize that the use of a water-gas shift catalyst in the
recirculated exhaust gas stream of a fuel-injected engine can be
carried out using different air/fuel ratio strategies and exhaust
gas recirculation system arrangements than those specifically
described. For example, the exhaust gas recirculation valve may be
a three-way valve disposed directly in the exhaust duct with a
first outlet port from which exhaust gas is discharged into the
ambient environment and a second outlet port through which exhaust
gas is directed to the EGR system. Such arrangements of the
apparatus and applications of the method embodying the present
invention are intended to fall within the scope of the following
claims.
[0033] Other aspects, features, and advantages of the present
invention may be obtained from a study of this disclosure and the
drawings, along with the appended claims.
* * * * *